Conductive MXene/Polymer Composites for Transparent Flexible Supercapacitors.

Transparent flexible energy storage devices are limited by the trade-off among flexibility, transparency, and charge storage capability of their electrode materials. Conductive polymers are intrinsically flexible, but limited by small capacitance. Pseudocapacitive MXene provides high capacitance, yet their opaque and brittle nature hinders their flexibility and transparency. Herein, the development of synergistically interacting conductive polymer Ti3C2Tx MXene/PEDOT:PSS composites is reported for transparent flexible all-solid-state supercapacitors, with an outstanding areal capacitance of 3.1 mF cm-2, a high optical transparency of 61.6%, and excellent flexibility and durability. The high capacitance and high transparency of the devices stem from the uniform and thorough blending of PEDOT:PSS and Ti3C2Tx, which is associated with the formation of O─H…O H-bonds in the composites. The conductive MXene/polymer composite electrodes demonstrate a rational means to achieve high-capacity, transparent and flexible supercapacitors in an easy and scalable manner.

Resilient and Tough Conductive Polymer Hydrogel for a Low-Hysteresis Strain Sensor.

Conductive polymer hydrogels are vital in strain sensors, yet achieving high resilience and toughness is a challenge. This study employs a prestretch method to engineer a tough conductive polymer hydrogel with sufficient resilience. Initially, a blend film of polyvinylalcohol (PVA) and ethylene-vinyl alcohol copolymer (EVOH) is prepared through solution casting, followed by a swelling process to form a PVA-EVOH hydrogel. This hydrogel, with PVA crystallites as crosslinking points, exhibits high toughness. The hydrogel is then immersed in pyrrole and ferric chloride solutions for in-situ polymerization of polypyrrole (PPy), creating a conductive PPy/PVA-EVOH hydrogel. Finally, a 200% prestretch is applied, breaking short chains within the network, eliminating energy dissipation at low strains. This results in a hydrogel with a 100% elastic deformation range, while maintaining high fracture toughness (1700 J m-2 ). The prestretched PPy/PVA-EVOH hydrogel functions as a strain sensor with low hysteresis, providing consistent strain measurements during loading and unloading. This outperforms the non-prestretched sample, which shows inconsistent responses between stretching and releasing.

Conductive Polymer-Based Interlayers in Restraining the Polysulfide Shuttle of Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) are considered a promising candidate for next-generation energy storage devices due to the advantages of high theoretical specific capacity, abundant resources and being environmentally friendly. However, the severe shuttle effect of polysulfides causes the low utilization of active substances and rapid capacity fading, thus seriously limiting their practical application. The introduction of conductive polymer-based interlayers between cathodes and separators is considered to be an effective method to solve this problem because they can largely confine, anchor and convert the soluble polysulfides. In this review, the recent progress of conductive polymer-based interlayers used in LSBs is summarized, including free-standing conductive polymer-based interlayers, conductive polymer-based interlayer modified separators and conductive polymer-based interlayer modified sulfur electrodes. Furthermore, some suggestions on rational design and preparation of conductive polymer-based interlayers are put forward to highlight the future development of LSBs.

An n-Type Open-Shell Conjugated Polymer with High-Spin Ground-State and High Intrinsic Electrical Conductivity.

Open-shell conjugated polymers with a high intrinsic conductivity and high-spin ground state hold considerable promise for applications in organic electronics and spintronics. Herein, two novel acceptor-acceptor (A-A) conjugated polymers based on a highly electron-deficient quinoidal benzodifurandione unit have been developed, namely DPP-BFDO-Th and DPP-BFDO. The incorporation of the quinoidal moiety into the polymers backbones enables deeply aligned lower-lying lowest unoccupied molecular orbital (LUMO) levels of below -4.0 eV. Notably, DPP-BFDO exhibits an exceptionally low LUMO (-4.63 eV) and a high-spin ground state characterized by strong diradical characters. Moreover, a self-doping through intermolecular charge-transfer is observed for DPP-BFDO, as evidenced by X-ray photoelectron spectroscopy (XPS) studies. The high carrier concentration in combination with a planar and linear conjugated backbone yields a remarkable electrical conductivity (σ) of 1.04 S cm-1 in the "undoped" native form, ranking among the highest values reported for n-type radical-based conjugated polymers. When employed as an n-type thermoelectric material, DPP-BFDO achieves a power factor of 12.59 µW m-1 K-2. Furthermore, upon n-doping, the σ could be improved to 65.68 S cm-1. This study underscores the great potential of electron-deficient quinoidal units in constructing dopant-free n-type conductive polymers with a high-spin ground state and exceptional intrinsic conductivity.

Selective separation of monovalent anions by PPy/pTS membrane electrodes in redox transistor electrodialysis.

Selective separation of nitrate over chloride is crucial for eutrophication mitigation and nitrogen resource recovery but remains a challenge due to their similar ionic radius and the same valence. Herein, a polypyrrole membrane electrode (PME) was fabricated by polymerization of pyrrole (Py) and p-toluenesulfonate (pTS), which was used as a working electrode in redox transistor electrodialysis. The anions in the source solution were first incorporated into the PME at reduction potentials and then released to receiving solution at oxidation potentials. Pulse widths and potentials were optimized to maximize the ion separation performance of PME, resulting in the improvement of NO3-/Cl- separation factor up to 6.93. The ion distributions in various depths of PME indicated that both NO3- and Cl- were incorporated into PME at negative potentials. Then, NO3- was preferentially released from PME at positive potentials, but most Cl- was retained. This was ascribed to the high binding energy between Cl- and PPy/pTS structure, which was 51.4% higher than that between NO3- and PPy/pTS structure. Therefore, the higher transport rate of NO3- in comparison with Cl- was achieved, leading to a high NO3- selectivity over Cl-. This work provides a promising avenue for the selective separation of nitrate over chloride, which may contribute to nitrogen resource recycling and reuse.

Nanostructured poly(thiophene acetic acid)/Au/poly(methylene blue) interface for electrochemical immunosensing of p53 protein.

A poly(thiophene acetic acid)/Au/poly(methylene blue) nanostructured interface was electrochemically assembled step-by-step on screen-printed carbon electrodes (SPCE) for label-free detection of p53 protein. The initial electrical conductive properties of the polymeric interface were increased with an additional layer of poly(methylene blue) electropolymerized in the presence of gold nanoparticles. The nano-immunosensing architecture was prepared by covalent immobilization of anti-p53 antibodies as bioreceptors through the poly(thiophene acetic acid) moieties. The nano-immunosensor assembly was extensively characterized by ultraviolet-visible spectrophotometry, dynamic and electrophoretic light scattering, scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, atomic force microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. Under optimal conditions, p53 was specifically and selectively detected by square wave voltammetry in a linear range between 1 and 100 ng mL-1 with a limit of detection of 0.65 ng mL-1. In addition, the electrochemical nano-immunosensor detected p53 in spiked human serum samples and colorectal cancer cell lysates, and the results were validated with a standard spectrophotometric method using a paired samples t test, which did not exhibit significant differences between both methods. The resultant p53 nano-immunosensor is simple to assemble, robust, and has the potential for point-of-care biomarker detection applications.

Induced Wettability Switch in Thin Films of Conductive Polymer Coatings Exhibiting Hydrophobic/Hydrophilic Interactions.

The hydrophobic/hydrophilic character of some conductive polymer (CP) coatings can be switched in the function of the working conditions of these adaptive materials. We studied the influence of electrical stimuli and intrinsic physical characteristics (nature of the polymerizable core, dopants, the droplet dimension and physical properties, surface roughness, etc.) on the CP wettability. A simulation strategy was developed for determining the contact angle (CA) of a liquid droplet on a CP layer with roughness. The method was tested for new reported CP composites, but with new dopants. The results indicate that the influences on the material wettability are correlated, and in practice, modification of more than one parameter converges to a wanted behavior of the material. E.g., the CP porous film of poly(3-hexylthiophene) (P3HT) + [6,6]-phenyl-C61-butyricacid-methyl-ester (PCBM) changes its wettability at voltages of up to 26 V, but if doping ions are inserted and the roughness geometry is modified, the voltage decreases twice. Our multi-parametrical study points out that the polymer wettability type is driven by the voltage, but this effect is tuned differently by each internal parameter. The thin films' effect and the dopants (in-situ and ex-situ) significantly decrease the actuation voltage. We also illustrated that the wettability type does not change for specific sets of parameters.

Electrochemical Properties of PEDOT:PSS/Graphene Conductive Layers in Artificial Sweat.

Electrodes based on PEDOT:PSS are gaining increasing importance as conductive electrodes and functional layers in various sensors and biosensors due to their easy processing and biocompatibility. This study investigates PEDOT:PSS/graphene layers deposited via spray coating on flexible PET substrates. The layers are characterized in terms of their morphology, roughness (via AFM and SEM), and electrochemical properties in artificial sweat using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The layers exhibit dominant capacitive behavior at low frequencies, with cut-off frequencies determined for thicker layers at 1 kHz. The equivalent circuit used to fit the EIS data reveals a resistance of about three orders of magnitude higher inside the layer compared to the charge transfer resistance at the solid/liquid interface. The capacitance values determined from the CV curves range from 54.3 to 122.0 mF m-2. After 500 CV cycles in a potential window of 1 V (from -0.3 to 0.7 V), capacitance retention for most layers is around 94%, with minimal surface changes being observed in the layers. The results suggest practical applications for PEDOT:PSS/graphene layers, both for high-frequency impedance measurements related to the functioning of individual organs and systems, such as impedance electrocardiography, impedance plethysmography, and respiratory monitoring, and as capacitive electrodes in the low-frequency range, realized as layered PEDOT:PSS/graphene conductive structures for biosignal recording.

Micropattern of Silver/Polyaniline Core-Shell Nanocomposite Achieved by Maskless Optical Projection Lithography.

With the development of device miniaturization, a flexible and fast preparation method is in demand for achieving microstructures with desired patterns. We develop a novel photoreduction-polymerization method for preparing conductive metal-polymer patterns. Ag/polyaniline (PANI) nanocomposites have been successfully synthesized by maskless optical projection lithography (MOPL) technology, which is based on multiphoton absorption and the localized surface plasmon resonance (LSPR) effect. The individualized design and synthesis of the nanocomposite patterns at the micro-nano scale are flexibly realized on a variety of substrates. The surface-enhanced Raman scattering (SERS) effect of Rhodamine 6G (R6G) is demonstrated on the microstructure of a square maze-shaped Ag/PANI nanocomposite. The electrical conductivity of the as-prepared nanocomposite is obtained. The preparation protocol proposed in this study opens up new avenues for the fabrication of micro-nano devices such as sensors and detectors.

Conductive Polymer Nanoparticles as Solid Contact in Ion-Selective Electrodes Sensitive to Potassium Ions.

A preparation method of nanocomposites based on poly (3-octylthiophene-2,5-diyl) (POT) and carbon black (CB) as the transducer of an all-solid potassium ion selective electrode is proposed. POT is used as the dispersant of CB, and the obtained nanocomposites have unique characteristics, including high conductivity, high capacitance and high stability. The potassium ion selective electrode based on POT and CB was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronopotentiometry. The results showed that the detection limit of potassium ions was 10-6.2 M, and the slope was 57.6 ± 0.8 mV/façade. The water layer test and anti-interference test show that the electrode has high hydrophobicity, the static contact angle reaches 139.7° and is not easily affected by light, O2 and CO2.

Review of Polymer-Based Composites for Electromagnetic Shielding Application.

The rapid advancement of electronic communication technology has greatly aided human productivity and quality of life, but it has also resulted in significant electromagnetic pollution issues. Traditional metals and alloys are often used for electromagnetic interference (EMI) shielding due to their excellent electrical conductivity. However, they have drawbacks such as being heavy, expensive, and having low corrosion resistance, which limits their application in electromagnetic shielding. Therefore, it is crucial to develop novel EMI shielding materials. Polymers, being highly flexible, corrosion-resistant, and possessing high specific strength, are frequently employed in electromagnetic shielding materials. In this review, we firstly introduce the basic theory of electromagnetic shielding. Then, we outline the processing methods and recent developments of polymer-based electromagnetic shielding composites, including uniform-, foam-, layered-, and segregated structures. Lastly, we present the challenges and prospects for the field, aiming to provide direction and inspiration for the study of polymer-based electromagnetic shielding composite materials.

Research Progress on Intrinsically Conductive Polymers and Conductive Polymer-Based Composites for Electromagnetic Shielding.

Electromagnetic shielding materials are special materials that can effectively absorb and shield electromagnetic waves and protect electronic devices and electronic circuits from interference and damage by electromagnetic radiation. This paper presents the research progress of intrinsically conductive polymer materials and conductive polymer-based composites for electromagnetic shielding as well as an introduction to lightweight polymer composites with multicomponent systems. These materials have excellent electromagnetic interference shielding properties and have the advantages of electromagnetic wave absorption and higher electromagnetic shielding effectiveness compared with conventional electromagnetic shielding materials, but these materials still have their own shortcomings. Finally, the paper also discusses the future opportunities and challenges of intrinsically conductive polymers and composites containing a conductive polymer matrix for electromagnetic shielding applications.

Semi-Polycrystalline Polyaniline-Activated Carbon Composite for Supercapacitor Application.

We report on the synthesis of activated carbon-semi-polycrystalline polyaniline (SPani-AC) composite material using in-situ oxidative polymerization of aniline on the carbon surface in an aqueous HCl medium at an elevated temperature of 60 °C. The electroactive polymeric composite material exhibits a uniformly distributed spindle-shaped morphology in scanning electron microscopy (SEM) and well-defined crystallographic lattices in the high-resolution transmission electron microscopy (TEM) images. The X-ray diffraction (XRD) spectrum reveals sharp peaks characteristic of crystalline polyaniline. The characteristic chemical properties of polyaniline are recorded using laser Raman spectroscopy. The cyclic voltammetry curves exhibit features of surface-redox pseudocapacitance. The specific capacitance calculated for the material is 507 F g-1 at the scan rate of 10 mV s-1. The symmetrical two-electrodes device exhibits a specific capacitance of 45 F g-1 at a current density of 5 A g-1. The capacitive retention calculated was found to be 96% up to 4500 continuous charge-discharge cycles and observed to be gradually declining at the end of 10,000 cycles. On the other hand, Coulombic efficiency was observed to be retained up to 85% until 4500 continuous charge-discharge cycles which declines up to 72% at the end of 10,000 cycles. The article also presents a detailed description of material synthesis, the formation of polyaniline (Pani) chains, and the role of material architecture in the performance as surface redox supercapacitor electrode.

Size-dependent electrophoretic motion of polystyrene particles at polyethylene glycol-dextran interfaces.

Currently, there is very limited information on the electrophoretic behavior of particles at a liquid-liquid interface formed by two conducting liquid solutions. Here, electrophoretic velocities of polystyrene particles at a polyethylene glycol (PEG)-dextran (DEX) interface were investigated in this paper. Experimental results show that the particle at the interface moves in the opposite direction to the applied electric field, with a velocity much lower than that in the PEG-rich phase and a litter larger than that in the DEX-rich phase. Similarly to the movement in Newtonian fluids, the velocity increases linearly with the increase in the applied electric field. Different to particle electrophoresis in Newtonian fluids, the velocities of the particles at the PEG-DEX interface increase linearly with the decrease in particle's diameters, implying a possible size-based particle differentiation at an interface.

Variations of tunnelling resistance between CNTs with strain in composites: non-monotonicty and influencing factors.

The electro-mechanical response of conductive carbon-nanotube(CNT)-polymer composites is vital when they are used as smart-sensing materials. Clarifying the variation trend of resistance with strain is the key to design and regulate the piezoresistive property of such material. Here, we present some finite element simulations to predict the electro-mechanical response using a geometrical model comprising two hollow cylindrical CNTs and a cuboid matrix. The electrical contact between CNTs is represented by some elements which account for quantum tunnelling effects and capture the sensitivity of conductivity to separation. Different from classical simulations using solid model or one-dimensional beam model, in which the tunnelling resistance between two CNTs changes monotonously with strain, the results in this work show that the trend is non-monotonic in some cases, i.e. it increases at first and then decreases with the uniaxial compressive strain when the elastic modulus of the matrix is high. In addition, factors affecting the different variation trends are discussed in details, which include geometric model, elastic modulus and Poisson's ratio of the matrix, and orientation angle.

Strain Sensing Behavior of 3D Printable and Wearable Conductive Polymer Composites Filled with Silane-Modified MWCNTs.

3D printing of conductive polymers is an attractive technique for achieving high flexibility, wearability, and sensing characteristics without geometrical limitations. However, there is an urgent need to integrate printability, conductivity, and sensing capability. Herein, a conductive polymer ink for 3D printing that combines the desirable features of high electrical conductivity, flexible stretchability, and strain-sensing monitoring is prepared. The ink matrix is polydimethylsiloxane and synergistically enhanced by acetylene carbon black (ACB) and multi-walled carbon nanotubes (MWCNTs) (silane or un-silane-modified). The inks are screened step-by-step to explore their printability, rheology, mechanical properties, and electrical performance upon loading. The formation of an electrically conductive network, electrical properties upon tensile load, and strain sensing stability under cyclic stretching are investigated intensively. It is demonstrated that conductive polymers filled by ACB and silane-modified, MWCNTs (MWCNTs-MTES) possess superior printability, stretchability, conductivity, and strain sensing behaviors. Finally, a flexible wearable strain-sensing skin patch is printed, and it successfully records joint motion signals on human fingers, wrists, and elbows with good stability and repeatability. Those results show the extent of potential applications in healthcare and motion monitoring fields. This work provides an efficient and simple route to achieve comfortably wearable and high-performance strain sensors.

Durable scalable 3D SLA-printed cuff electrodes with high performance carbon + PEDOT:PSS-based contacts.

BACKGROUND: The stimulation and recording performance of implanted neural interfaces are functions of the physical and electrical characteristics of the neural interface, its electrode material and structure. Therefore, rapid optimization of such characteristics is becoming critical in most clinical and research studies. This paper describes the development of an upgraded 3D printed cuff electrode shell design containing a novel intrinsically conductive polymer (ICP) for stimulation and recording of peripheral nerve fibers. METHODS: A 3D stereolithography (SLA) printer was used to print a scalable, custom designed, C-cuff electrode and I-beam closure for accurate, rapid implementation. A novel contact consisting of a percolated carbon graphite base electrodeposited with an intrinsically conductive polymer (ICP), poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) produced a PEDOT:PSS + carbon black (CB) matrix that was used to form the electrochemical interface on the structure. Prototype device performance was tested both in-vitro and in-vivo for electrical chemical capacity, electrochemical interfacial impedance, surgical handling, and implantability. The in-vivo work was performed on the sciatic nerve of 25 anesthetized Sprague Dawley rats to demonstrate recording and stimulating ability. RESULTS: Prototypes of different spatial geometries and number of contacts (bipolar, tripolar, and tetrapolar) were designed. The design was successfully printed with inner diameters down to 500 µm. Standard bipolar and tripolar cuffs, with a 1.3 mm inner diameter (ID), 0.5 mm contact width, 1.0 mm pitch, and a 1.5 mm end distance were used for the functional tests. This geometry was appropriate for placement on the rat sciatic nerve and enabled in-vivo testing in anesthetized rats. The contacts on the standard bipolar electrode had an area of 2.1 × 10-2  cm2 . Cyclic voltammetry on ICP coated and uncoated graphite contacts showed that the ICP increased the average charge storage capacity (CSC) by a factor of 30. The corresponding impedance at 1 Hz was slightly above 1 kΩ, a 99.99% decrease from 100 kΩ in the uncoated state. The statistical comparison of the pre- versus post-stimulation impedance measurements were not significantly different (p-value > 0.05). CONCLUSIONS: The new cuff electrode enables rapid development of cost-effective functional stimulation devices targeting nerve bundles less than 1.0 mm in diameter. This allows for recording and modulation of a low-frequency current targeted within the peripheral nervous system.

CNT/Graphite/SBS Conductive Fibers for Strain Sensing in Wearable Telerehabilitation Devices.

Rapid growth of personal electronics with concurrent research into telerehabilitation solutions discovers opportunities to redefine the future of orthopedic rehabilitation. After joint injury or operation, convalescence includes free active range of movement exercises, such as joints bending and straightening under medical supervision. Flexion detection through wearable textile sensors provides numerous potential benefits such as: (1) reduced cost; (2) continuous monitoring; (3) remote telerehabilitation; (4) gamification; and (5) detection of risk-inducing activities in daily routine. To address this issue, novel piezoresistive multi-walled carbon nanotubes/graphite/styrene-butadiene-styrene copolymer (CNT/Gr/SBS) fiber was developed. The extrusion process allowed adjustable diameter fiber production, while being a scalable, industrially adapted method of manufacturing textile electronics. Composite fibers were highly stretchable, withstanding strains up to 285%, and exhibited exceptional piezoresistive parameters with a gauge factor of 91.64 for 0-100% strain range and 2955 for the full scope. Considering the composite's flexibility and sensitivity during a series of cyclic loading, it was concluded that developed Gr/CNT/SBS fibers were suitable for application in wearable piezoresistive sensors for telerehabilitation application.

Wide-Range Humidity-Temperature Hybrid Flexible Sensor Based on Strontium Titanate and Poly 3,4 Ethylenedioxythiophene Polystyrene Sulfonate for Wearable 3D-Printed Mask Applications.

In this paper, we report a fast, linear wide-range hybrid flexible sensor based on a novel composite of strontium titanate (SrTiO3) and poly 3,4 ethylenedioxythiophene polystyrene sulfonate (PEDOT: PSS) as a sensing layer. Inter-digitate electrodes (IDEs) were printed for humidity monitoring (finger: 250 µm; spacing: 140 µm; length: 8 mm) whilst a meander-based pattern was printed for the temperature measurement (meander thickness: 180 µm; spacing: 400 µm) on each side of the PET substrate using silver ink. Moreover, active layers with different concentration ratios were coated on the electrodes using a spray coating technique. The as-developed sensor showed an excellent performance, with a humidity measurement range of (10-90% RH) and temperature measurement range of (25-90 °C) with a fast response (humidity: 5 s; temperature: 4.2 s) and recovery time (humidity: 8 s; temperature: 4.4 s). The reliability of the sensor during mechanical bending of up to 5.5 mm was validated with a reliable performance. The sensor was also used in real-world applications to measure human respiration. For this, a suggested sensor-based autonomous wireless node was included in a 3D-printed mask. The manufactured sensor was an excellent contender for wearable and environmental applications because of its exceptional performance, which allowed for the simultaneous measurement of both quantities by a single sensing device.

Wearable Sensor Based on Flexible Sinusoidal Antenna for Strain Sensing Applications.

A flexible sinusoidal-shaped antenna sensor is introduced in this work, which is a modified half-wave dipole that can be used for strain sensing applications. The presented antenna is an improved extension of the previously introduced antenna sensor for respiration monitoring. The electrical and radiative characteristics of the sinusoidal antenna and the effects of the geometrical factors are studied. An approach is provided for designing the antenna, and equations are introduced to estimate the geometrical parameters based on desired electrical specifications. It is shown that the antenna sensor can be designed to have up to 5.5 times more sensitivity compared to the last generation of the antenna sensor previously introduced for respiration monitoring. The conductive polymer material used to fabricate the new antenna makes it more flexible and durable compared to the previous generation of antenna sensors made of glass-based material. Finally, a reference antenna made of copper and an antenna sensor made of the conductive polymer are fabricated, and their electrical characteristics are analyzed in free space and over the body.